A theranostic microneedle array patch for integrated glycemia sensing and self-regulated release of insulin

Diabetes can cause various complications and affect the normal functioning of the human body. A theranostic and diagnostic platform for real-time glycemia sensing and simultaneous self-regulated release of insulin is desired to improve diabetic patients' life quality. Here, we describe a theranostic microneedle array patch, which enables the achievement of visualization quantification of glycemia and simultaneously self-regulated release of insulin. The microneedle patch (MNDF) was fabricated by crosslinking of 3-aminophenylboronic acid (ABA)-modified sodium alginate and chondroitin sulfate. The hierarchical structure consisted of a tip part containing mineralized insulin particles and glucose oxidase (GOD) for insulin release, and a base surface embodying 3,3',5,5'-tetramethylbenzidine (TMB) and (horseradish peroxidase) HRP for real-time glycemia sensing. In the presence of glucose, GOD converts glucose into H⁺ and H₂O₂, driving gradual dissolution of the calcium layer of insulin particles, resulting in long-acting release of insulin. By the bio-catalytic action of HRP, the generated H₂O₂ brings about a visible color change allowing the glucose level at the base surface to be read out. We believe that the theranostic microneedle array patch can act as a promising alternative for future clinical applications.